Windscreen wiper blade harness assemblies typically include a plurality of levers or yokes pivotally connected together to form flexible, articulated lever assemblies. The axes where the yokes are pivotally connected become points of corrosion and sources of noise. Heretofore diverse forms of plastic spacers inserted at the pivotal joint have been devised to prevent the above mentioned problems. Such spacers should be of sufficient strength to avoid breakage at the stress points resulting from the relatively severe torsional and tensile loading which is applied in normal use as the wiper traverses a to and fro path with sudden reversals at each end of the wiper stroke. It is desirable to maintain the cross section as thin as possible for economy of materials, maintenance of minimum harness profile and size. The minimum size of the harness is important to avoid excess weight which results in additional load on the power source and also to avoid obstruction to the operator's view. The larger the cross section of the spacer, the larger the harness lever cross section must be to accomodate it. Furthermore, since the wipers are a highly visible accessory it is desirable to avoid an awkward appearance. Ease of assembly is another important requisite.
An example of a prior art plastic spacer is disclosed in U.K. Pat. No. 1,183,446 published Mar. 4, 1970 in which a first part U-shaped in cross section and a similarly shaped insert are nested in spaced apart relationship and connected together at the end of the leg portion. The said first part and insert are so spaced as to define a U-shaped recess between them. This recess is dimensioned to receive a similarly cross sectioned end of a yoke. Pairs of projections extend inwardly and outwardly from the legs of the insert, the outward projections being received in openings of a harness main yoke and the inward projections engaging in openings of an auxiliary yoke to pivotally secure the yokes to each other. The inward and outward projections on each leg are displaced relative to each other to be out of alignment. It is not possible to provide the usual ears employed in this type of blade harness for accomodating the openings in the main yoke because the end of the blade must fit into the channel shaped recess, thus necessitating the offset positions of the projections.
Offsetting the projections exposes the spacer to shear stresses during operation which could cause fracturing of the walls unless the wall section is relatively thick.